Process for isomerizing a feed stream including one or more C4-C6 hydrocarbons

ABSTRACT

One exemplary embodiment can be a process for isomerizing a feed stream including one or more C4-C6 hydrocarbons. The process may include contacting the feed stream in an isomerization reaction zone with an isomerization catalyst at isomerization conditions to produce an isomerization zone effluent; passing at least a portion of the isomerization zone effluent to a stabilizer zone and recovering a stabilizer overhead stream, a bottom stream, and a stripper feed stream; passing the stripper feed stream to a stripping zone and separating the stripper feed stream into a stripper overhead stream and a stripper bottom stream; and recycling at least a portion of the stripper bottom stream to a deisopentanizer zone and passing a stream from the deisopentanizer zone to the isomerization reaction zone. Usually, the stabilizer overhead stream includes one or more C5 −  hydrocarbons, the bottom stream includes at least about 85%, by weight, one or more C6 +  hydrocarbons, and a stripper feed stream including at least about 10%, by weight, one or more C5 +  hydrocarbons. Often, a stripper overhead stream includes at least about 5%, by weight, one or more C4 −  hydrocarbons and a stripper bottom stream includes at least about 90%, by weight, one or more C5 +  hydrocarbons.

FIELD OF THE INVENTION

This invention generally relates to a process for isomerizing, and moreparticularly, a process for isomerizing a feed stream including one ormore C4-C6 hydrocarbons.

DESCRIPTION OF THE RELATED ART

Normally, a traditional gasoline blending pool includes C4⁺ hydrocarbonshaving boiling points of less than about 205° C. at atmosphericpressure. This range of hydrocarbons may include C4-C6 paraffins and,particularly C5-C6 normal paraffins that can have relatively low octanenumbers. To improve octane, isomerization may rearrange the structure ofthe paraffinic hydrocarbons into branched-chain paraffins. Often, octaneupgrading commonly uses isomerization to convert C6 and lighter boilinghydrocarbons.

Typically, isomerization units for C5 and C6 hydrocarbons may have ahigh C5 content that may limit octane, particularly if the equilibriumC5 isomerization ratio is reached in the reactor. Usually, adeisopentanizer column can be positioned in front of the isomerizationunit to remove isomerized C5 hydrocarbons in the fresh feed allowing ahigher conversion of the normal C5 hydrocarbons-rich isomerizationreactor feed. However, the fresh feed normal pentane conversion toisopentane may be limited without recycling isomerized C5 hydrocarbonsfrom the product. Utilization of sieves on the product can remove thenormal pentane and permit their recycle, however such installations aregenerally capital intensive and require significant utilities. As aconsequence, there is generally a desire to provide a mechanism that isless capital intensive and lowers utility utilization to permit therecycling of these materials.

SUMMARY OF THE INVENTION

One exemplary embodiment can be a process for isomerizing a feed streamincluding one or more C4-C6 hydrocarbons. The process may includecontacting the feed stream in an isomerization reaction zone with anisomerization catalyst at isomerization conditions to produce anisomerization zone effluent; passing at least a portion of theisomerization zone effluent to a stabilizer zone and recovering astabilizer overhead stream, a bottom stream, and a stripper feed stream;passing the stripper feed stream to a stripping zone and separating thestripper feed stream into a stripper overhead stream and a stripperbottom stream; and recycling at least a portion of the stripper bottomstream to a deisopentanizer zone and passing a stream from thedeisopentanizer zone to the isomerization reaction zone. Usually, thestabilizer overhead stream includes one or more C5⁻ hydrocarbons; thebottom stream includes at least about 85%, by weight, one or more C6⁺hydrocarbons; and a stripper feed stream including at least about 10%,by weight, one or more C5⁺ hydrocarbons. Often, a stripper overheadstream includes at least about 5%, by weight, one or more C4⁻hydrocarbons and a stripper bottom stream includes at least about 90%,by weight, one or more C5⁺ hydrocarbons.

Another exemplary embodiment may be a process for isomerizing a feedstream having one or more C4-C6 hydrocarbons. The process can includecontacting the feed stream in an isomerization reaction zone with anisomerization catalyst at isomerization conditions to produce anisomerization zone effluent; passing at least a portion of theisomerization zone effluent to a stabilizer column and recovering astabilizer overhead stream, and a bottom stream; passing the stabilizeroverhead stream to a receiver; withdrawing a receiver bottom stream fromthe receiver and providing at least a portion as a stripper feed stream;and recycling a stripper bottom stream to a deisopentanizer zone andpassing a stream from the deisopentanizer zone to the isomerizationreaction zone. The stabilizer overhead stream may include one or moreC5⁻ hydrocarbons, and a bottom stream may include at least about 85%, byweight, one or more C6⁺ hydrocarbons. The stripper feed stream caninclude at least about 10%, by weight, one or more C5⁺ hydrocarbons, andthe stripper bottom stream can include at least about 90%, by weight,one or more C5⁺ hydrocarbons to a deisopentanizer zone.

Yet another exemplary embodiment can be a process for isomerizing a feedstream including one or more C4-C6 hydrocarbons. The process may includecontacting the feed stream in an isomerization reaction zone with anisomerization catalyst at isomerization conditions to produce anisomerization zone effluent; passing at least a portion of theisomerization zone effluent to a stabilizer column and recovering astabilizer overhead stream, a bottom stream, and a side-stream; passingat least a portion of the side-stream to a stripper column; andrecycling a stripper bottom stream to a deisopentanizer zone and passinga stream from the deisopentanizer zone to the isomerization reactionzone. A stabilizer overhead stream may include one or more C5⁻hydrocarbons, a bottom stream may include at least about 85%, by weight,one or more C6⁺ hydrocarbons, and a side-stream may include at leastabout 85%, by weight, one or more C5⁺ hydrocarbons. Also, the stripperbottom stream can include at least about 90%, by weight, one or more C5⁺hydrocarbons.

Generally, the embodiments disclosed herein can allow the addition of astripping zone to separate an isomerization zone effluent into separatestreams. Particularly, a stripper overhead stream can include at leastabout 5%, by weight, one or more C4⁻ hydrocarbons and a stripper bottomstream comprising at least 90%, by weight, one or more C5⁺ hydrocarbons.The stripper bottom stream can be recycled to a deisopentanizer zonethat can further separate isopentanes from normal pentanes. As aconsequence, such a configuration can allow the efficient recycling ofone or more C5 hydrocarbons, while minimizing the recycling of C4⁻hydrocarbons and allowing a recovery of normal pentanes for recyclingthrough the isomerization zone. Thus, the embodiments disclosed hereincan provide an improved process for recycling one or more C5hydrocarbons in an isomerization zone without having an undue increasein energy and capital expenses.

DEFINITIONS

As used herein, the term “stream” can include various hydrocarbonmolecules, such as straight-chain, branched, or cyclic alkanes, alkenes,alkadienes, and alkynes, and optionally other substances, such as gases,e.g., hydrogen, or impurities, such as heavy metals, and sulfur andnitrogen compounds. The stream can also include aromatic andnon-aromatic hydrocarbons. Moreover, the hydrocarbon molecules may beabbreviated C1, C2, C3 . . . Cn where “n” represents the number ofcarbon atoms in the one or more hydrocarbon molecules. Furthermore, asuperscript “+” or “−” may be used with an abbreviated one or morehydrocarbons notation, e.g., C3⁺ or C3⁻, which is inclusive of theabbreviated one or more hydrocarbons. As an example, the abbreviation“C3⁺” means one or more hydrocarbon molecules of three carbon atomsand/or more.

As used herein, the term “zone” can refer to an area including one ormore equipment items and/or one or more sub-zones. Equipment items caninclude one or more reactors or reactor vessels, heaters, exchangers,pipes, pumps, compressors, and controllers. Additionally, an equipmentitem, such as a reactor, dryer, or vessel, can further include one ormore zones or sub-zones.

As used herein, the term “rich” can mean an amount of at least generallyabout 50%, and preferably about 70%, by mole, of a compound or class ofcompounds in a stream.

As used herein, the term “substantially” can mean an amount of at leastgenerally about 80%, and preferably about 90%, by mole, of a compound orclass of compounds in a stream.

As used herein, the terms “alkane” and “paraffin” may be usedinterchangeably.

As used herein, the term “overhead stream” can mean a stream withdrawnat or near a top of a column, typically a distillation column.

As used herein, the term “bottom stream” can mean a stream withdrawn ator near a bottom of a column, typically a distillation column.

As depicted, process flow lines in the figures can be referred to,interchangeably, as, e.g., lines, pipes, streams, feeds, effluents, andproducts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of an exemplary isomerate manufacturingzone.

FIG. 2 is a schematic depiction of another version of the exemplaryisomerate manufacturing zone.

DETAILED DESCRIPTION

Referring to FIG. 1, an exemplary isomerate manufacturing zone 100 caninclude a deisopentanizer zone 140, an isomerization reaction zone 180,a stabilizer zone 200, and a stripping zone 300. Zones for isomerizingC4-C6 hydrocarbons are disclosed in, e.g., Nelson A. Cusher, UOP PenexProcess and UOP Par-Isom Process, The Handbook of Petroleum RefiningProcesses, 3rd edition, Robert A. Myers, editor, 2004, pp. 9.15-9.27 andpp. 9.41-9.45, as well as, e.g., U.S. Pat. No. 5,326,926, U.S. Pat. No.7,223,898 B2, and U.S. Pat. No. 7,514,590 B1.

A feed stream 120 can include a hydrocarbon fraction having one or moreC4-C6 normal paraffins. Such hydrocarbon fractions are disclosed in,e.g., U.S. Pat. No. 7,223,898 B2. The hydrocarbon fractions can includeC4-C6 normal paraffins, and optionally rich in C4-C6 normal paraffins.One exemplary hydrocarbon fraction has substantially pure normalparaffins having from 4-6 carbon atoms. Other hydrocarbon fractions mayinclude a light natural gasoline, a light straight run naphtha, a gasoil condensate, a light raffinate, a light reformate, a lighthydrocarbon, a field butane, and a straight-run distillate havingdistillation end points of about 77° C. and optionally containingsubstantial quantities of one or more C4-C6 paraffins. The feed stream120 may also contain low concentrations of unsaturated hydrocarbons andhydrocarbons having more than 6 carbon atoms.

In one exemplary embodiment, the feed stream 120 can include:

TABLE 1 (in percent, by weight) RANGE C4⁻ C5 C6 C7⁺ General 0-2 10-9010-90 0-15 Typical 0.5 40-60 40-60 2

The feed stream 120 can be combined with a recycle stream 324, ashereinafter described, to form a combined feed 124, and its compositionmay vary among chemical manufacturing plants and refineries. Thecombined feed 124 can be provided to a deisopentanizer zone 140.Generally, the deisopentanizer zone 140 can include a deisopentanizercolumn 150. The deisopentanizer column 150 can provide an overheadstream 154 including at least about 85%, by weight, one or more C5hydrocarbons, such as isopentane, which can be utilized as an isomerateproduct. The bottom stream 158 from the deisopentanizer zone 140 can beprovided to the isomerization reaction zone 180.

If a halided, such as a chlorided, catalyst is utilized, the bottomstream 158 can pass through a dryer 164 before entering theisomerization reaction zone 180. Typically, the isomerization reactionzone 180 can also receive a make-up gas stream 162 that may pass througha dryer 168 and a chloride stream 170. An exemplary isomerizationreaction zone 180 is disclosed in, e.g., U.S. Pat. No. 7,223,898. Insuch an isomerization reaction zone 180, the gas often separated in thestabilizer zone 200, as hereinafter described, can be scrubbed prior tobeing discharged.

The isomerization reaction zone 180 can include one or more exemplarycatalysts disclosed in, e.g., U.S. Pat. No. 7,223,898 B2 and U.S. Pat.No. 5,326,926. The combined feed 124 may be contacted in theisomerization reaction zone 180 with an isomerization catalyst. Such acatalyst can be a halided catalyst, such as a chlorided platinum aluminacatalyst. The alumina can be an anhydrous gamma-alumina, although otheraluminas may be utilized. In addition to platinum, the catalyst mayoptionally include one or more of palladium, germanium, ruthenium,rhodium, osmium, and iridium. The catalyst may contain from about0.1-about 0.25%, by weight, platinum, and optionally about 0.1-about0.25%, by weight, one or more of palladium, germanium, ruthenium,rhodium, osmium, and iridium, based on the weight of the catalyst. Suchan exemplary catalyst is disclosed in, e.g., U.S. Pat. No. 5,326,926.

If a non-halided catalyst is utilized, the dryers 164 and 168 and thechloride stream 170 can be omitted. Particularly, the bottom stream 158can proceed directly to the isomerization reaction zone 180 withoutdrying. In addition, the make-up gas stream 162 can also pass directlyto the isomerization zone absent drying. Catalysts incorporated in suchzones are disclosed in, e.g., U.S. Pat. No. 7,223,898 B2.

Another suitable isomerization catalyst is a solid strong acid catalyst,which may include a sulfated support of an oxide or hydroxide of a GroupIVB (IUPAC 4) metal, preferably a zirconium oxide or hydroxide, at leasta first component of a lanthanide element or yttrium, and at least asecond component being a platinum-group metal component. The Group IVB(IUPAC 4) metal may include titanium, zirconium, halfnium, and dubnium.The catalyst optionally contains an inorganic-oxide binder, such asalumina.

The support material of the solid strong acid catalyst can include anoxide or a hydroxide of a Group IVB (IUPAC 4) metal. In one exemplaryembodiment, the Group IVB element is zirconium or titanium. Sulfate maybe composited on the support material. A component of alanthanide-series element can be incorporated into the composite usingany suitable means. The lanthanide series element component may be oneor more of lanthanum, cerium, praseodymium, neodymium, promethium,samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium,thulium, ytterbium and lutetium. A suitable amount of the lanthanideseries component may be about 0.01-about 10%, by weight, on an elementalbasis, based on the weight of the catalyst. A platinum-group metalcomponent may be added to the catalytic composite by any suitable means,such as impregnation. The platinum-group metal component may be one ormore of platinum, palladium, ruthenium, rhodium, iridium, and osmium, inan amount of about 0.01-about 2%, by weight, of the platinum-group metalcomponent, on an elemental basis based on the weight of the catalyst.

Optionally, the catalyst is bound with a refractory inorganic oxide. Thebinder, when employed, usually comprises from about 0.1-about 50%,preferably about 5-about 20%, by weight, based on the weight of thefinished catalyst. The support, sulfate, metal components and optionalbinder may be composited in any order effective to prepare a catalystuseful for the isomerization of hydrocarbons. Examples of suitableatomic ratios of lanthanide or yttrium to platinum-group metal may be atleast about 1:1; preferably about 2:1. Optionally, the catalyst mayfurther include a third component of iron, cobalt, nickel, rhenium or amixture thereof. As an example, iron may be present in an amount ofabout 0.1-about 5%, by weight, on an elemental basis based on the weightof the catalyst. In one exemplary embodiment, the solid strong acidisomerization catalyst may be sulfated zirconia or a modified sulfatedzirconia.

The isomerization reaction zone 180 can operate at any suitableconditions depending on the composition of the combined feed 124 andcatalyst type. As an example, operating conditions within theisomerization reaction zone 180 may be selected to maximize theproduction of isoalkanes. A temperature within the isomerizationreaction zone 180 usually ranges from about 40-about 235° C. and apressure usually ranges from about 700-7,000 KPa. The feed rate to theisomerization reaction zone 180 can also vary over a wide range,including a liquid hourly space velocity ranging from about 0.5-about 12hr⁻¹.

The isomerization effluent 184 may be sent to the stabilizer zone 200 toseparate the desired isomerized products from hydrogen, light ends,lower octane isomerized products, and cyclohexane plus heavyhydrocarbons having 7 or more carbon atoms. The stabilizer zone 200 caninclude a stabilizer column 220, a receiver 250 and a reboiler 224. Thestabilizer column 220 can operate under suitable conditions forproviding a C5 recycle stream to the deisopentanizer zone 140. In thismanner, the following table discloses typical operating parameters forone exemplary embodiment having the stabilizer column 220 in conjunctionwith an isomerization reaction zone 180 containing a non-halidedcatalyst:

TABLE 2 Parameter General Preferred Optimal Operating Pressure  790-2,100 1,100-1,500 1,200-1,420 (kPa) Bottoms 140-210 170-200 NotApplicable Temperature (° C.) Stabilizer Trays 25-75 35-60 40-50Stabilizer Reflux/Feed 0.5-3   1.0-2.5 1.5-2.0 Molar Ratio

The stabilizer bottoms temperature may change significantly due to thepresence of heavier hydrocarbons, such as C7⁺ hydrocarbons, present inthe feed, i.e., isomerization zone effluent 184 to the stabilizer column220.

Typically, the stabilizer column 220 can produce an overhead stream 240that may pass to the receiver 250, where one or more C5⁻ hydrocarbonsmay separate as a gas stream 262 and be scrubbed for a halidedisomerization catalyst or recycled for a non-halided isomerizationcatalyst. A receiver bottom stream 254 can be split into a reflux stream258 and a stripper feed 284, which will be described hereinafter. Abottom stream 226 from the stabilizer column 220 can be split into areboiling stream 228 and a product stream 234. The reboiling stream 228can pass through the reboiler 224 and be heated with any suitableheating stream 232, such as a pressurized steam or a process stream.Typically, the bottom stream 226 can include at least about 85%, byweight, one or more C6⁺ hydrocarbons. The product stream 234 can becombined with the overhead stream 154 from the deisopentanizer zone 140to form a combined product for, e.g., a gasoline blending pool.

The stripper feed 284, which may be a portion from the receiver bottomstream 254 of the receiver 250, can pass to the stripping zone 300. Thestripper feed 284 can include at least about 10%, by weight, one or moreC5⁺ hydrocarbons. The stripping zone 300 can include a stripper column304 having a reboiler 316 that can provide a stripper overhead stream308 and a stripper bottom stream 312. Generally, the stripper overheadstream 308 includes at least about 5%, by weight, one or more C4⁻hydrocarbons. The stripper overhead stream 308 can be combined with thestabilizer overhead stream 240 that is provided to the receiver 250 andmay include at least about 10%, by weight, one or more C5⁻ hydrocarbons.The stripper bottom stream 312 can be split into a stripper reboilingstream 320 and the net stripper bottom stream or stripper recycle stream324 and include at least about 90%, by weight, one or more C5⁺hydrocarbons. Typically, the stripper column 304 is operated to providethe stripper recycle stream 324 that has low levels of C4⁻ hydrocarbons.As depicted, the stripper column 304 typically includes the reboiler316, but may not include a condenser and a receiver.

In this manner, the following table discloses typical operatingparameters for one exemplary embodiment having the stripper column 304in conjunction with an isomerization reaction zone 180:

TABLE 3 Parameter General Preferred Bottoms Temperature (° C.) 115-160130-145 Stripper Column Trays  5-30 10-20

The stripper reboiling stream 320 can pass through the reboiler 316which can be provided with a heating stream 322. The heating stream 322can use any suitable heat source, such as another process stream or apressurized steam. The stripper reboiling stream 320 can be returned tothe stripper column 304.

Exemplary compositions for streams in the isomerate manufacturing zone100 as depicted in FIG. 1 can be as follows:

TABLE 4 (in percent, by weight, based on weight of the stream) TotalStream Range C4⁻ C5 iC5 nC5 C6 C7⁺ 154 General 0-5 —   85-99.5 0.1-15 <0.1 <0.1 Typical 1  — 95 5 <0.1 <0.1 158 General <0.1 —  1-10 10-8010-95 0-15 Typical <0.1 — 2-3 30-60 40-70 2-5  262 General 80-98 2-20 —— — — Typical 90-95 5-10 — — — — 284 General 50-80 — 10-30  2-10 1-3<0.1 Typical 65-75 — 18-23 4-8 1-2 <0.1 324 General 0.5-4  — 60-80 15-25 2-15 <0.1 Typical 0.8-1.2 — 65-75 20-25 4-8 <0.1 234 General 0-2 0-10 —— 80-95 1-10 Typical <0.1 0-5  — — 92-94 2-5 

Referring to FIG. 2, another exemplary version of the isomeratemanufacturing zone 100 is depicted. In this exemplary embodiment, thestripping zone 300 receives a stripper feed 284 as a side-stream fromthe stabilizer column 220. As discussed above in FIG. 1, anisomerization zone effluent 184 can be provided to the stabilizer zone200. The isomerization zone effluent 184 is provided to the stabilizercolumn 220 and produces the stabilizer overhead stream 240 and thebottom stream 226. The stabilizer overhead stream 240 passes to thereceiver 250 and provides a gas stream 262 that can be scrubbed orrecycled as discussed above, and the receiver bottom stream 254. Aportion of the receiver bottom stream 254 can be removed as a stream 264with another portion provided as the reflux stream 258. Any suitabletray within the stabilizer column 220, typically within the toptwo-fifths, or even top third, of the trays in the stabilizer column220, can have the stripper feed 284 withdrawn as a side-stream from atray 222. The stripper feed 284 may be provided to the stripper column304, as discussed above, and may include at least about 10%, or even atleast about 70% or about 85%, by weight, one or more C5⁺ hydrocarbons.Generally, the purpose of the stripper column 304 is to strip C4⁻hydrocarbons to provide the net stripper bottom stream 324 containingpredominantly C5 one or more hydrocarbons for recycling to theisomerization reaction zone 180. Usually, the stripper overhead stream308 can be returned to the stabilizer column 220 while the stripperbottom stream 312 is split as the stripper reboiling stream 320 and thestripper recycle stream 324, which is combined with the feed stream 120.The bottoms of the stabilizer column 220 may operate as discussed above.In this exemplary embodiment, withdrawing the side-stream can allow theseparation of C5 hydrocarbons for recycling to the isomerizationreaction zone 180. Moreover, utilizing the recycle to thedeisopentanizer zone 140 can remove isopentane before the bottom stream158 enters the isomerization reaction zone 180. Although not depicted inthe drawings, all columns depicted may be associated with otherequipment, such as reboilers, condensers, and heat exchangers.

In operation, it is generally desired to operate the stabilizer column220 and the stripper column 304 at such conditions to provide themaximum amount of C5 hydrocarbons to the combined feed 124. Exemplaryoperating conditions for stabilizer column 220 and the stripper column304 are depicted above.

Exemplary compositions for streams in the isomerate manufacturing zone100 as depicted in FIG. 2 without stream 264 can be as follows:

TABLE 5 (in percent, by weight, based on weight of the stream) TotalStream Range C4⁻ C5 iC5 nC5 C6 C7⁺ 154 General 0-5 —   85-99.5 0.1-15 <0.1 <0.1 Typical 1  — 95 5 <0.1 <0.1 158 General <0.1 —  1-10 10-8010-95 0-15 Typical <0.1 — 2-3 30-60 40-70 2-5  262 General 80-98 2-20 —— — — Typical 90-95 5-10 — — — — 284 General  1-15 — 60-80 10-30  1-15<0.1 Typical 3-9 — 65-75 16-22 2-7 <0.1 324 General 0.5-5  — 60-80 10-30 2-15 <0.1 Typical 0.5-2  — 65-75 18-25 4-8 <0.1 234 General <0.1 0-10 —— 80-95 1-10 Typical <0.1 0-5  — — 92-94 2-5 

Exemplary compositions for streams in isomerate manufacturing zone 100as depicted in FIG. 2 with stream 264 can be as follows:

TABLE 6 (in percent, by weight, based on weight of the stream) TotalStream Range C4⁻ C5 iC5 nC5 C6 C7⁺ 154 General 0-5 —   85-99.5 0.1-15 <0.1 <0.1 Typical 1  — 95 5 <0.1 <0.1 158 General <0.1 —  1-10 10-8010-95 0-15 Typical <0.1 — 2-3 30-60 40-70 2-5  262 General  95-100 0-5 —— — — Typical  98-99.5 0-2 — — — — 284 General  1-15 — 60-80 10-30  1-15<0.1 Typical 3-8 — 68-78 15-25 2-7 <0.1 324 General 0.5-5  — 60-80 10-30 1-15 <0.1 Typical 0.5-2  — 68-78 15-25 2-8 <0.1 234 General <0.1  0-15— — 80-95 1-10 Typical <0.1 2-8 — — 90-94 2-5  264 General  90-100  0-10— — <0.1 <0.1 Typical 97-99 1-3 — — <0.1 <0.1In this exemplary embodiment with a non-halided catalyst, there istypically no need to remove halide compounds such as hydrogen chloride.As a result, the stream 264 may be taken as a product.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The preceding preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

In the foregoing, all temperatures are set forth in degrees Celsius and,all parts and percentages are by weight, unless otherwise indicated.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

The invention claimed is:
 1. A process for isomerizing a feed streamcomprising one or more C4-C6 paraffins, comprising: A) contacting thefeed stream in an isomerization reaction zone with an isomerizationcatalyst at isomerization conditions to produce an isomerization zoneeffluent; B) passing at least a portion of the isomerization zoneeffluent to a stabilizer zone and recovering a stabilizer overheadstream comprising one or more C5⁻ hydrocarbons, a bottom streamcomprising at least about 85%, by weight, one or more C6⁺ hydrocarbons,and a stripper feed stream comprising at least about 85%, by weight, oneor more C5⁺ hydrocarbons; C) passing the stripper feed stream to astripping zone and separating the stripper feed stream into a stripperoverhead stream comprising at least about 5%, by weight, one or more C4hydrocarbons and a stripper bottom stream comprising at least about 90%,by weight, one or more C5⁺ hydrocarbons; and D) passing at least aportion of the stripper bottom stream to a deisopentanizer zonecomprising a deisopentanizer column; and E) passing a bottom stream fromthe deisopentanizer column to the isomerization reaction zone.
 2. Theprocess according to claim 1, wherein the isomerization reaction zonecomprises a chlorided platinum alumina catalyst or a sulfated zirconiacatalyst.
 3. The process according to claim 1, wherein the isomerizationreaction zone comprises a catalyst, in turn, comprising a supportcomprising a sulfated oxide or hydroxide of at least one element oftitanium, zirconium, halfnium, and dubnium; a first component of atleast one element of a lanthanide series and yttrium; and a secondcomponent of at least one element of platinum, palladium, ruthenium,rhodium, iridium, and osmium.
 4. The process according to claim 1,wherein the isomerization reaction zone comprises a catalyst, in turn,comprising an alumina, a platinum, and a chloride.
 5. The processaccording to claim 1, wherein the stripping zone comprises a strippercolumn, and the stripper bottom stream upon exiting the stripper columnis at a temperature of about 115-about 160° C.
 6. The process accordingto claim 5, wherein the stabilizer zone comprises a stabilizer column,and the bottom stream exiting the stabilizer column is at a temperatureof about 140-about 210° C.
 7. The process according to claim 6, whereinthe stabilizer column operates at a pressure of about 790-about 2,100kPa.
 8. The process according to claim 1, wherein the stabilizer zonecomprises a stabilizer column and a receiver wherein the receivercollects an overhead stream from the stabilizer column, and at least aportion of the stripper feed stream is provided from the receiver. 9.The process according to claim 8, wherein the stripper feed stream iswithdrawn from a tray at a top third of the stabilizer column.
 10. Theprocess according to claim 1, wherein the process further compriseswithdrawing an overhead stream comprising at least about 85%, by weight,one or more C5 hydrocarbons from the deisopentanizer column.
 11. Aprocess for isomerizing a feed stream comprising one or more C4-C6paraffins hydrocarbons, comprising: A) contacting the feed stream in anisomerization reaction zone with an isomerization catalyst atisomerization conditions to produce an isomerization zone effluent; B)passing at least a portion of the isomerization zone effluent to astabilizer column and recovering a stabilizer overhead stream comprisingone or more C5⁻ hydrocarbons, and a bottom stream comprising at leastabout 85%, by weight, one or more C6⁺ hydrocarbons; C) passing thestabilizer overhead stream to a receiver; D) withdrawing a receiverbottom stream from the receiver and providing at least a portion as astripper feed stream comprising at least about 85%, by weight, one ormore C5⁺ hydrocarbons; E) passing the stripper feed stream to astripping zone and separating the stripper feed stream into a stripperoverhead stream comprising at least about 5%, by weight, one or more C4hydrocarbons and a stripper bottom stream comprising at least about 90%,by weight, one or more C5⁺ hydrocarbons; and F) passing at least aportion of the stripper bottom stream comprising at least about 90% byweight one or more C5⁺ hydrocarbons to a deisopentanizer zone comprisinga deisopentanizer column; and G) passing a bottom stream from thedeisopentanizer column to the isomerization reaction zone.
 12. Theprocess according to claim 11, wherein the isomerization reaction zonecomprises a catalyst, in turn, comprising a support comprising asulfated oxide or hydroxide of at least one element of titanium,zirconium, halfnium, and dubnium; a first component of at least oneelement of a lanthanide series and yttrium; and a second component of atleast one element of platinum, palladium, ruthenium, rhodium, iridium,and osmium.
 13. The process according to claim 11, wherein theisomerization reaction zone comprises a catalyst, in turn, comprising analumina, a platinum, and a chloride.
 14. The process according to claim11, wherein the stripper bottom stream upon exiting a stripper column isat a temperature of about 115-about 160° C.